Alloys of sintered carbides



United States Patent 3,463,621 ALLOYS 0F SINTERED CARBIDES Richard Kiefier, Vienna, Austria, assignor to Societe des Poudres Metalliques et des Alliages Speciaux Ugine- Carbone, Paris, France, a corporation of France No Drawing. Filed June 19, 1968, Ser. No. 738,137

Claims priority, application Austria, June 20, 1967,

A 5,750/67 Int. Cl. B22f 3/10 US. Cl. 29--182.7 11 Claims ABSTRACT OF THE DISCLOSURE An improved sintered hard metal alloy comprising 4 to 15 percent of at least one metal selected from the group consisting of iron, nickel and cobalt, 0.5 to 75 percent titanium carbide, 3 to 40 percent columbium carbide-hafnium carbide and the balance tungsten carbide. A small amount (0.1 to 0.5 percent) of vanadium carbide may be included.

My invention relates to sintered hard metal alloys and, in particular, to sintered hard metal alloys used in fabricating tools for machining materials to produce long or short chips.

In the past, sintered hard metals used in machining materials that produce short chips were comprised of tungsten carbide and cobalt to which small quantities (at least 3 percent) of additional carbides such as titanium carbide, tantalum carbide, columbium carbide or vanadium carbide were frequently added. For machining materials that produce long chips, tungsten carbide-titanium carbide alloys were used in Europe and tungsten carbide-tantalum carbide alloys were used in the United States. More recently, it has become common practice to utilize an alloy of tungsten carbide-titanium carbide-tantalum carbide and cobalt. These alloys contain from to percent titanium carbide plus tantalum carbide for machining soft steels and cast steels, and from 15 to 30 percent titanium carbide plus tantalum carbide for machining harder steels. For finished machining and high cutting speeds, these alloys contain from 30 to 50 percent or more titanium carbide and tantalum carbide. For finished machining and high cutting speeds, alloys with titanium carbide contents of 70 percent have been used. (All percentages referred to herein are percent by weight.)

It is a well-known fact that tantalum carbide increases the heat resistance of the tungsten carbide-titanium carbide cobalt alloys as well as their strength. This is achieved even though tantalum carbide is a relatively soft carbide, having a Vickers hardness of 1500 to 1600, as compared to tungsten carbide and titanium carbide which have Vickers hardness of 2200 to 2400 and 3000, respectively. Attempts have been made to substitute equal amounts of columbium carbide for tantalum carbide, since it has a Vickers hardness of 2200 to 2400. However, it has been possible to replace only 30 percent of the tantalum carbide with the columbium carbide, since any larger addition causes embrittlement of the alloy. Attempts have also been made to substitute hafnium carbide for tantalum carbide (see Hartmetalle by Kieffer and Benesovsky) which have been successful.

This invention provides novel sintered hard metal alloys which can be used in fabricating tools for machining materials that produce both long and short chips. The invention also encompasses a method of making the alloys and tools fabricated from the alloys. The alloys of my invention comprise from 4 to 15 percent of at least one metal belonging to the iron group consisting of iron, nickel and cobalt, but preferably cobalt, 0.5 to 75 percent titani- 3,463,621 Patented Aug. 26, 1969 um carbide, 3 to 40 percent columbium carbide and hafmum carbide preferably as a mixed crystal and the balance tungsten carbide. The alloy may also contain up to 0.5 percent vanadium carbide and possibly a small percentage of tantalum carbide, which will generally be in the columbium carbide-hafnium carbide mixed crystal. Preferably, however, the alloy contains 6 to 11 percent of at least one metal belonging to the iron group consisting of non, nickel and cobalt, but preferably cobalt, 5 to 40 percent titanium carbide, and 5 to 20 percent columbium carbide-hafnium carbide as mixed crystals or in solid soluuon. If vanadium carbide is included, it is preferably between 0.2 and 0.3 percent. The tantalum carbide will generally not exceed 3 percent.

By replacing the tantalum carbide with columbium carbide-hafnium carbide in tungsten carbide-titanium carbide-tantalum carbide-cobalt alloys, it has been possible to increase the hardness or the bending strength of the alloy, and at times, to increase both of these properties. These results are contrary to those to be expected in that both columbium carbide and hafnium carbide are harder than pure tantalum carbide or tantalum carbide containing small amounts of columbium carbide.

Alloys producing particularly good machining performance are those in which the amount of hafnium carbide 1s approximately /5 to 3 times that of the columbium carbide (i.e., HfC is 20 to percent of the mixed crystal). Furthermore, it is often preferable that the hafnium carbide be /5 to 1 times the columbium carbide (HfC is 20 to 50 percent of the mixed crystal). In a long series of tests it has been shown that particularly good cutting metal alloys were produced which were superior to the well-known alloys with tantalum carbide.

The manufacture of the alloys is advantageous since the costly separation of columbium and tantalum is not required. It is possible to use columbium minerals having a low tantalum content, such as A to 75 of the columbium content, for the direct manufacture of columbium carbide, since the presence of corresponding amounts of tantalum carbide in the columbium carbide does not alter the properties of the alloys of the invention. Further, it is also possible to use large amounts of columbic acid containing small amounts of tantalum which arise in the separation of columbium from tantalum and in the enrichment of tantalum. These products, which up until now have served almost exclusively only in the manufacture of ferrocolumbium, therefore, have a new and novel market.

The columbium carbide-hafnium carbide solid solutions may be added, at least in part, in the form of ternary columbium carbide-hafnium carbide-tungsten carbide mixed crystals or columbium carbide-hafnium carbidetitanium carbide mixed crystals, or in the form of quarternary columbium carbide-hafnium carbide-titanium carbide-tungsten carbide mixed crystals. At the time of the preparation of these mixed crystals, 20 to 40 percent of the tungsten carbide and/or the titanium carbide can be added. Therefore, significant self-purification can be obtained in the usual way as far as oxygen and nitrogen are concerned. Such mixed crystals have, for example, the following composition:

50 parts NbC, 50 parts HfC, 40 parts WC,

or 70 parts NbC, 30 parts HfC, 20 parts WC,

or parts TiC, 40 parts WC, 20 parts NbC, 40 parts HfC.

It has also been proven practical to add 0.1 to 0.5 percent, and preferably 0.2 to 0.3 percent vanadium carbide to the basic alloy.

In the preparation of alloys of my invention, I prefer to add columbium carbides and hafnium carbides, and

possibly tungsten carbides and titanium carbides, wholly or in part, in the form of grains the size of which is less than 1 micron, and preferably less than 0.1 micron.

The following compositions illustrate alloys of my invention which are intended for machining materials pro- 4 to 15 percent of at least one metal selected from the group consisting of iron, nickel and cobalt, 0.5 to 75 percent titanium carbide, 3 to 40 percent columbium carbide-hafnium carbide mixed crystal, up to 0.5 percent Vanadium carbide, and the balance tungsten carbide and minor duclng long chips: amounts of tantalum carbide and mcldental lmpurities.

2. An alloy as set forth in claim 1 wherein the ratio of TiC NbG Hro TaC we hafnium carbide to columbium carbide is to 3. $333? 3% i $352 Effififi {$353 3. An alloy as set forth in claim 1 in which the tantalum carblde is no greater than /5 the amount of columbium 6 3 3 10 Remainder. 16 7 3 8 D0 carblde. 1s 5 a 2 7 Do. 4. An alloy as set forth in claim 1 having 4 to percent 18 4 6 9 Do. b It 25 s 5 9 D0. 3 0 5 3 2 7 5. A smtered carbide alloy consisting essentially of 6 v 15 to 11 percent of at least one metal selected from the group 2111c fifnovlflng COIIIPOSIUOHS 4? WP alloys of consisting of iron, nickel and cobalt, 5 to 40 percent titalllventlofl Intended for machlnmg mammals Produclng nium carbide, 5 to percent hafnium carbide-columbium Short chlpsl carbide mixed crystal, and the balance of said alloy tung- T sten carbide. T'C NbO Hi0 a0 00 W0 (percelnt (percent (percent (percent (percent (percent 20 6. An alloy as set forth 1n claim 5 1nclud1ng 0.2 to 0.3 by wt.) by wt.) by wt.) by wt.) by wt.) by wt.) P rcent vanadium carbide.

0. 5 2 L 5 o- 5 6 Remainder. 7. An alloy as set forth in claim 5 wherein said hafnium 1 1 2 5 Do. carbide-columblum carbide mixed crystal comprises from 20 to 50 percent hafnium carbide. The following table shows the bending strength and 8. An alloy as set forth in claim 6 including up to 3 perhardness of the hard metal alloys produced according to cent tantalum carbide. my invention as compared with standard tungsten car- 9. A sintered carbide alloy consisting essentially of 6 bide-titanium carbide-tantalum carbide (columbium carto 11 percent cobalt, 5 to 40 percent titanium carbide, 5 bide) cobalt alloys. As is shown, it is evident that my to 20 percent columbium carbide-hafnium carbide-tantaalloys exhibit superiority with respect to the bending and 30 lum carbide mixed crystal, and the balance tungsten carhardening strength of the metal alloys. bide.

TABLE 1 HV/60 Bending Viekers strength, hardness, TiO Co WC NbC(TaC)+HiC kg./m1n. kgJmm.

Known alloys 16 7 Best 8 TaO 115-125 1, 500-1, 600 16 7 do 6TaC+2NbC 110-120 1, 550-1, 650 Alloys of the in- 16 7 do 6NbC+2 Hi0 120-130 1, 650-1, 750 vention. 1s 7 do 4NbC+2TaC+2HiC 120-130 1, 550-1, 650 16 7 do 4NbC+4 HfC 140-150 1, 600-1, 700 16 7 do 2NbC+6 Hto 130-140 1, soc-1,700

T10 NbC Hi0 V0 00 W0 (percent (percent (percent (percent (percent (percent by wt.) by wt.) by wt.) by wt.) by Wt.) by wt.)

5 3 2 0. 2 11 Remainder. 12 8 4 0. 2 8. 5 D0.

While I have described certain preferred embodiments of my invention, it should be understood that it may otherwise be embedded within the scope of the appended claims.

I claim:

1. A sintered carbide alloy consisting essentially of 5 10. An alloy as set forth in claim 9 including 0.2 to 0.3 percent vanadium carbide.

11. In a sintered hard metal alloy consisting essentially of tungsten carbide, titanium carbide and at least one metal selected from the group consisting of iron, nickel and cobalt, the improvement comprising the addition of 3 to 40 percent columbium carbide-hafnium carbide mixed crystal.

References Cited UNITED STATES PATENTS 2,188,983 2/1940 Padowicz 29182.7 2,198,343 4/1940 Kieffer 29-l82.7 2,899,739 8/1959 Ohlsson 29--l82.7 2,924,875 2/ 1960 Gisner et al. 75-203 X 3,245,763 4/ 1966 Ohlsson 29-182.7

BENJAMIN R. PADGETT, Primary Examiner ARTHUR J. STEINER, Assistant Examiner US. Cl. X.R. 

